Fluted cable

ABSTRACT

A cable includes at least one elongated groove formed in the insulation around a conductor to provide radial and helical passages for impregnation by a viscous material such as wax. This is used for wire-guided devices connected to insulated conductors which are wound on reels of multi-layer close helical coils. The wax temporarily holds the turns together to permit the conductor to be paid off from the center of the reel without disturbing adjacent turns. The grooves permit the wax to penetrate into the gaps between the helical insulated conductors.

. I United States Patent 1 1 11 3,783,180

Spicer 1' Jan. 1, 1974 FLUTE!) CABLE 3,100,136 8/1963 DAscoli 174/110 PM [75] Inventor: Lyndon Reginald Spicer, FO PATENTS OR APPLICATIONS Llandevaud wales 106,535 2 1939 Australia 317 260 [73] Assignee: International Standard Electric cm'porafion New York Primary ExaminerE. A. Goldberg [221 Filed: June 13, 1972 Att0rney--C. Cornell Remsen, Jr. et a1.

[21] A l.No.: 262 383 pp 57 ABSTRACT [30] Foreign A li ti Priority D t A cable includes at least one elongated groove formed Jul-y 15 1971 Great Britain N 33189 H] in the insulation around a conductor to provide radial and helical passages for impregnation by a viscous ma- 5 CL 174/110 R, 174/98 242/173 terial such as wax. This is used for wire-guided devices 336/205 connected to insulated conductors which are wound 511 int. c1. ..l-l01b 7/00 reels of mum-layer close helical coih- The [58] Field of Search 174/110 R, 110 PM, temporarily holds the turns together Permit the 174/25 R, 336/205; 242/173, 172; 317/260 conductor to be paid off from the center of the reel without disturbing adjacent turns. The grooves permit [56] References Cited the wax to penetrate into the gaps between the helical UNITED STATES PATENTS insulated conductors.

3,077,514 2/1963 Kang l74/1 10 PM 4 Claims, 3 Drawing Figures 1 FLUTED CABLE BACKGROUNDOF THE INVENTION 1. Field of the Invention This invention relates to an elongated member, such as an insulated electrical conductor, which is so shaped that when it is wound in a close helical coil form with many layers, and impregnated with a viscous adherent material such as wax, it can be paid off in a controlled manner from the center of the coil under a given load without disturbing adjacent turns of the coil.

2. Description of the Prior Art Insulated electrical conductors wound into multilayer coils and impregnated with a wax in such a manner that they can be paid off from the center of the coil in a controlled manner may be used, for example, in connection with wire-guided weapons. The wound coil is impregnated with a wax under a vacuum in order to effectively stick the turns ofthe coil together until they are paid off. When the cross-section of the insulated conductor is circular, the wax, which is liquid during application, has to flow along the helical paths between the insulated conductors in the coil. This is a timeconsuming and awkward process even under vacuum conditions, and it is possible that the coil will not be completely impregnated due to the presence of air locks.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an insulated electrical conductor which can be wound into such a helical coil and which is of such a cross-section that impregnation of the coil with a viscous adherent material such as wax is facilitated.

According to the present invention there is provided a close helical multi-layer coil formed from an elongated memberhaving a cross-section which is substantially circular and having at least one groove extending along its length, wherein the gaps between the turns of the coiled elongated. member are filled with a wax, the groove permitting both radial and helical impregnation of wax into, the coil.

Embodiments of the present invention will now be described with reference to the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a section through a portion of multi layer helically-formed impregnated coil of an insulated conductor having longitudinal grooves provided along its length,

FIG. 2 shows a portion of a single insulated conductor having the longitudinal grooves, and

FIG. 3 shows a helical multi-layer coil on a reel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment of elongated member shown in FIGS. 1 and 2 comprises an electrical conductor 1 of, for example, plain copper, insulated by extruded plastics material 2 of, for example, high-density polyethylene, to a cross-section that is substantially circular but which is provided with, for example, four equi-spaced semi-circular recesses 3. The insulated conductor therefore, has four equi-spaced grooves extending along its length. The grooves may take a longitudinal or helical path with respect to the axis of the conductor in the surface of the insulation 2.

When such an insulated conductor is wound in many layers in a close helical coil, a cross-sectional portion of which is shown in FIG. 1, instead of there being no passage between the spaces in adjacent layers of conductor, as in the case of circularly cross-sectioned insulated conductors, passages such as 4 are provided. The

passages depend upon the orientation of the grooves 3. When such a coil is impregnated under vacuum with a viscous adherent material such as wax 6, therefore, the wax does not have to purely follow the helical path between the conductors since it can also pass through radial passages such as 4. The grooves 3, therefore, provide paths whereby the wax impregnation takes place in a radial as well as helical manner, thus assisting the impregnation process. In addition, the presence of the grooves 3 provides a larger cross-section for wax flow between the turns along the helical paths than without them, as can be ascertained from the shape of the gap at 5, and this also assists in the wax impregnation of the coil.

In the embodiment shown in FIGS. 1 and 2 four grooves 3 are provided, but improved impregnation will be obtained with one or more grooves in comparison with no grooves at all, although the degree of improvement will vary.

Whilst the invention has been described with reference to insulated electrical conductors, the elongated member may alternatively for example, be in the form of a cord, that is purely comprise extruded plastics material, which can be wound on a reel 7, such as shown in FIG. 3, into a multi-layer close helical coil 8 that can be paid-off from its center in a controlled manner. The grooves 3 can alternatively, have cross-sections other than a semicircle. The wax for impregnation of the coil may alternatively be other viscous adherent materials such as polyisobutylene or waterbased emulsions.

It is to be understood that the foregoing description of specific examples of this invention is made by way of example only and is not to be considered as a limitation on its scope.

What is claimed is:

1. A close wound helical multi-layer coil comprising a continuous elongated member of solid extruded insulating material having a cross-section which is substantially circular and having a plurality of separate parallel grooves spaced around the outer peripheral surface, each of said grooves extending continuously along the full length of said member, said member including a continuous elongated electrical conductor embedded in said insulating material, said member and conductor being wound into a coil including a plurality of close wound adjacent turns and layers of turns having gaps between the outer peripheral surfaces of said adjacent turns, and a viscous adherent material filling said gaps, said grooves providing both radial and helical passages between adjacent turns and layers for impregnation of said viscous material into said coil, said viscous material being solid at a predetermined temperature to hold said coil turns together until being paid-off.

2. The coil as claimed in claim 1, wherein said viscous adherent material is wax.

3. The coil as claimed in claim 1, wherein said electrical conductor is copper and said insulating material is polyethylene.

4. The coil as claimed in claim 1, including four grooves equispaced in helical paths around said insulating material. 

1. A close wound helical multi-layer coil comprising a continuous elongated member of solid extruded insulating material having a cross-section which is substantially circular and having a plurality of separate parallel grooves spaced around the outer peripheral surface, each of said grooves extending continuously along the full length of said member, said member including a continuous elongated electrical conductor embedded in said insulating material, said member and conductor being wound into a coil including a plurality of close wound adjacent turns and layers of turns having gaps between the outer peripheral surfaces of said adjacent turns, and a viscous adherent material filling said gaps, said grooves providing both radial and helical passages between adjacent turns and layers for impregnation of said viscous material into said coil, said viscous material being solid at a predetermined temperature to hold said coil turns together until being paid-off.
 2. The coil as claimed in claim 1, wherein said viscous adherent material is wax.
 3. The coil as claimed in claim 1, wherein said electrical conductor is copper and said insulating material is polyethylene.
 4. The coil as claimed in claim 1, including four grooves equispaced in helical paths around said insulating material. 